Climate change emerged as a topic of public and political concern in the 1980s alongside the discovery of the ‘Antarctic Ozone Hole.’ The issue was raised up the political agenda in the latter half of the 1980s by scientists and international administrators operating in a transnational setting –culminating in the eventual formation of the Intergovernmental Panel on Climate Change (IPCC) in 1988. Created to produce a comprehensive assessment of the science, impacts and possible response strategies to climate change, the Panel managed to bridge to the two worlds of science and politics as a hybrid science-policy organisation, meeting the divergent needs of a variety of groups, specifically in the US Government. This thesis will provide an analysis of the negotiations that resulted in the formation of the IPCC in 1988. In particular, I examine the power politics of knowledge production in the relationship between a transnational set of scientists engaged in assessments of climate change and national policymakers. I argue that the IPCC was established as a means of controlling who could speak for the climate, when and how, and as such the Panel legitimised and privileged certain voices at the expense of others. In addition to tracing and examining the history of international climate change assessments in the 1980s, I will scrutinise how the issue became a topic of international political concern. Focusing on the negotiations between the World Meteorological Organization (WMO), United Nations Environment Programme (UNEP) and the United States of America in the formation of the IPCC, I will argue against the received view that the U.S. has consistently been in a battle with climate science and the IPCC. As I will show that the U.S. government was both integral to the decision to establish the IPCC and also one of its strongest backers. Following the formation of the Panel I examine the ad hoc decisions taken and processes adopted during the First Assessment (AR1) that contributed to the anchoring of the IPCC as the central authority on climate related knowledge. As such I show that in the absence of any formal procedural guidance there was considerable leeway for the scientists and Working Group Chairs to control and shape the content of the assessment. Finally, I analyse the ways in which U.S. and UK policymakers strategically engaged with the Panel. Significantly, I show that the ways in which the U.S. pushed all political debates to the heart of the scientific assessment imparted a linear approach to policymaking –assessment precedes and leads the policymaking –contributing to the increasing entanglement of the science and politics of climate change. Moreover, the narrow technical framing of the issue and the largely tokenistic attempts to involve participants from developing countries in the IPCC resulted in the UN resolutions (backed by developing countries) establishing the Intergovernmental Negotiating Committee/United Nations Framework Convention on Climate Change (INC/UNFCC) contrary to the wishes of U.S. policymakers.